
Abby L.
asked 05/24/13What are the answers to -4+sin(x)=-8+sqrt2/2
I need to know how to find the two answers between 0 and 2 pi. I need the answers in degrees, not radians. there should be two answers
2 Answers By Expert Tutors

George C. answered 05/24/13
Humboldt State and Georgetown graduate
sin x = (e^ix – e^-ix)/2i
Let sin x = -4 + sqrt2/2 = k = (e^ix – e^-ix)/2i
2ik = (e^ix – e^-ix)
(e^ix – e^-ix) –2ik = 0
e^2ix – 2ike^ix –1 = 0
Let u = e^ix
u^2 – 2iku – 1 = 0, u = (2ik ± (((-2ik)^2 – 4(1)(-1))^(1/2))/2
(-2.586i ± 1.64)/2
u= e^ix ≈ -.4735i, -2.113i
e^ix = -.4735i
ix = ln(-.4735i)
ix = ln(.4735) - (pi)/2
x = -i ln(.4735) – (pi)/2
x = -i(-.748) + (pi)/2
x = -1.57 + .748i
|x| = 1.739, Θ = arctan (.748/-1.57) = 154.5° OR 334.5º
AND
e^ix = -2.113i
ix = ln (-2.113i)
ix = ln (2.113) – ipi/2
x = -i ln (2.113) + (pi)/2
x = -1.57 - .748i
|x| = 1.739, Θ = 25.5° OR 205.5°

Nataliya D. answered 05/24/13
Patient and effective tutor for your most difficult subject.
l sin(x) l ≤ 1 ---> -1 ≤ sin(x) ≤ 1
sin (x) = -4 + (√2)/2 ---> sin(x) ≈ - 3.3 < - 1 , sin(x) is not exist there
~~~~~~~~~~
[0, 360o]
sin x = (√2)/2 ----> x1 = 45o and x2 = 135o
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Nataliya D.
Hi Abby. You have to understand the order of operations! There is huge difference between -4 + sin(x) = -8 + v2/2 and
-4 + sin(x) = (-8 + v2) / 2 !!!!!!!
The answer for first one is empty set of numbers, and for another one:
sin(x) = -4 + v2/2 + 4
sin(x) = v2/2 ---> x1 = 45o and x2 = 135o on the segment [0, 2pi].
05/24/13